Objective and sensitive methods to detect subtle brain dysfunction resulting from concussion is needed. According to reports from the U.S. Military, blast concussion brain injury is the most significant proportion of current casualties in Iraq and Afghanistan. However, inadequate preparation and clinical tools to recognize and properly treat such casualties increases the profile of these injuries and their aftereffects. The brain performs the most complex and essential processes in the human body. Surprisingly, contemporary health care lacks sophisticated tools to objectively assess their function. A patient's mental and neurological status is typically assessed clinically by an interview and a subjective physical exam. A typical clinical laboratory currently has no capacity to assess brain function or pathology, contributing little more than identification of poisons, toxins, or drugs that may have externally impacted the CNS. These laboratories can diagnose possible concussions, through the physical exam, but determining the severity of the concussion cannot be done with any accuracy.
Brain imaging studies, such as computed tomography imaging (CT), magnetic resonance imaging (MRI), are widely used and useful. These structural and anatomical tests, however, reveal little information about brain function. The “functional MRI” (fMRI) is a recent improvement over MRI. fMRI testing provides relative images of the concentration of oxygenated hemoglobin in various parts of the brain. While the concentration of oxygenated hemoglobin, which shows the usage of oxygen, is a useful indication of the gross metabolic function of specific brain regions, it provides very limited or no information about the underlying brain function, i.e., the processing of information by the brain, which is electrochemical in nature.
For example, an injured brain part can be using a “normal” amount of oxygen. An fMRI will thus not be able to diagnose a condition or injury which may be dramatically dysfunctional. Moreover, in the immediate time following an acute traumatic brain injury (TBI), such as a concussion, CT and MRI/fMRI imaging studies are typically negative, revealing no structural abnormalities, even when there is clear and dramatically abnormal brain function. The same is also true of diffuse axonal injury (DAI), related to shearing of nerve fibers which is present in the majority of concussive brain injury cases, and can remain invisible on most routine structural images. Swelling or edema from DAI resulting from a concussion can subsequently lead to coma and death.
Further, CT and MRI/fMRI testing devices are completely unavailable in portable, field-deployable applications, due to their size, power requirements and cost. These assessment tools play an important role in selected cases, but they are costly, not universally available, and they do not provide critical information at the early stages of acute care situations. Current technologies are unable to provide the immediate, actionable information critical to timely intervention, appropriate triage, or the formulation of an appropriate plan of care for acute brain trauma such as a concussion. However, the brain has the least capacity for repair among organs, and thus time sensitive triage and intervention is very important in treating brain injuries such as concussions.
All of the brain's activity, whether reflexive, automatic, unconscious, or conscious, is electrical in nature. Through a series of electrochemical reactions, mediated by molecules called neurotransmitters, electrical potentials (voltages) are generated and transmitted throughout the brain, traveling continuously between and among the myriad of neurons. This activity establishes the basic electrical signatures of the electroencephalogram (EEG) and creates identifiable frequencies which have a basis in anatomic structure and function. Understanding these basic rhythms and their significance makes it possible to characterize the EEG as being within or beyond normal limits. At this basic level, the EEG serves as a signature for both normal and abnormal brain function.
The electrical activity of the brain has been studied extensively since the first recordings over 75 years ago, and especially since the advent of computers. “Normal” electrical activity of the brain has been well characterized in hundreds of studies, with a narrow standard deviation. The frequencies of electrical activity of some parts of the brain are the normal response to various stimuli, such as acoustic, visual, or pain, known as “evoked potentials.”
Evoked potentials (EP) are particular waves that have characteristic shapes, amplitudes and duration of peaks within those wave shapes, and many other features, all of which have well established normative data, generated over decades of research. Normative data for all of the EEG and evoked response waves are remarkably constant across different genders, ages, and ethnicities. Moreover, any variability that does exist is well described and explained.
Neuroscientists have also characterized the EEG signature of various different brain pathologies. Just as an abnormal electrocardiogram (ECG) pattern is a strong indication of a particular heart pathology, an irregular brain wave pattern is a strong indication of a particular brain pathology such as concussion. A large body of data, with continuing refinements and contributions, constitutes the field of clinical neurophysiology.
Even though EEG-based neurometric technology is accepted today and a tremendous body of data exists, application in the clinical environment is notably limited. Some of the barriers limiting its adoption include: the cost of EEG equipment, its lack of portability, the need for a technician to administer the test, the time it takes to conduct the test, and the need for expert interpretation of the raw data. More importantly, the technology is neither available nor practical in the acute care setting, especially at the point of care. A complete diagnostic EEG instrument typically costs $80,000, fully equipped. Despite the high costs, the instrument produces essentially raw waveforms which must be carefully interpreted by an expert. Moreover, use of the standard EEG equipment remains extremely cumbersome. It can take 30 minutes or more to apply the required 19 electrodes. Once a subject is prepared for the test, the EEG recording can take from 1 to 4 hours. Data is collected and analyzed by an EEG technician, and is then presented to a neurologist for interpretation and clinical assessment. There are some self-standing dedicated neurodiagnostic laboratories which focus strictly on detailed analysis of electrical brain data. Neither the specialized centers, nor the typically large hospital EEG machines are practical for the ER, operating room (OR), intensive care unit (ICU), or any other acute care medicine setting where patients are in the greatest need.
Studies conducted by medical professionals worldwide have highlighted the need for developing a way to provide an early diagnosis and effective treatment for patients who have suffered a traumatic head injury, in particular, a concussion. Head injuries, such as a concussions, may have serious long term effects. For example, one of the largest threats posed by a concussion is delayed brain swelling caused by fiber shearing, which, if left untreated, can cause coma and death. When properly diagnosed, concussions may be treated using different treatment options, but each of the treatments includes its own risk, and should be administered based on the severity of the injury. Immediate, functional concussion detection is needed to treat patients with possible concussions for the prevention of further damage and disability.
Many times, despite the need for early detection, concussions often go undetected, particularly when a subject is not exhibiting any visible wounds. CT scans and MRI images have less than a 60% accuracy for the detection of a concussion, and are limited in tracking progress of the concussion and guiding treatment. Electrical signals emitted by the brain, however, may be an accurate detector of concussion and its' aftereffects, usually having an accuracy of 90-95%. Moreover, monitoring the brain's electrical signals may also be used to monitor the progress of the concussion over time allowing for excellent treatment management.